3D-printing is a method where a powder layer is distributed on a surface. An inkjet printer is used to distribute a binder on the surface to create a temporary bond between the particles. The binder is dried and the process is repeated until a powder bed containing an object bound together with the binder is created. The lose powder is rinsed or cleared from the object and the object is then sintered. The boundaries between the original powder layers disappear and a solid object is created.
Advantages with 3D printing compared to other layer manufacturing methods are the high speed, no need to build support structures and that the final object is homogenous without residual stresses. The high speed comes from the deposition of the powder layer in one step and that the binder can be deposited with several nozzles simultaneously. Other methods that can build objects by dispensing at each point or use a single laser or electron beam spot for selective solidification are inherently slower since they can only build at one point at a time. The powder bed supports the structure making it possible to build structures containing arches without building a separate support structure that has to be removed in a later step. The powder can be deposited without density gradients and this secures that the sintering done in a separate stage can create homogenous object without differential shrinkage.
In the original 3D-printing invention (Cima U.S. Pat. No. 6,146,567) the powder was applied on the surface by spraying a suspension. In a later invention by Fcubic the powder is spread in the dry form to create a layer (Fcubic WO03055628). The latter method is very fast but it is limited to coarser powders with approximately 10-20 μm particle size that can be spread homogenously in the dry state. Finer powders, this includes most sinterable ceramic powders and hard metal powders, are impossible to spread in the dry state in a homogenous thin layer due to van der Waals attraction that inhibits the flow of dry small particles.
Microsystems are increasingly used to make products smarter, that is to add new functionally to products. They are for example used in products like solar cells, batteries, OLED, microwave components, lab-on-a chip and high temperature sensors, vehicles and kitchen appliances. Microsystems can contain sensors that sense (acceleration, radiation, force, pressure, moisture, chemical environment etc) they can also contain actuators based on electrostatic, magnetostrictive, piezoelectric and other principles.
To date it has not been possible to use layered manufacturing to directly fabricate Microsystems packaging with true 3D structures. Available methods such as LTCC (low temperature cofired ceramics) can only supply flat substrates where the electronic connection (vias) have to be placed perpendicular to the layers. This often makes it necessary to combine LTCC structures with other 3D-structures manufactured separately. Using additive and direct manufacturing to build the package would create a competitive advantage. Developing of integrated electronic chips is a very efficient streamlined production process done by silicon foundries. The packaging is however not standardized in the same way. Packaging is often the major cost in production of Microsystems. Further design, fabrication and testing of packaging are very time consuming processes.
The electrical interconnects for Microsystems are built with an insulating and an electrically conducting material. For some applications other materials are required to build resistors and to modify the dielectric properties. For optical interconnects, other material combinations are required to build waveguides. This requires that the fabrication process can build with and integrate several materials. This has not been possible in previously available methods for layered manufacturing.